Randy,

Are you loosing these impellers do to lack of water?
Maybe it is time to put in a manifold with a check valve for all the times you are flying through the air. You would have more of a buffer instead of running them dead dry as soon as the boat leaves the water...

We ran such a system on our triple engine outboard cat. The manifold kept water pressure to all 3 engines, even if one or two engines weren't picking up water from it's gearcases.

I don't know what your rules state in regards to water pickups.
But I can see a hull mounted pick up with a manifold and check valve maybe fixing your issue....

Do you know any plumbers ??? :drink:

Another thing to look for...Casting slag in the housing. We have found in many of the housings, enough sharp edges to tear up an impellor instantly.